Method for dehydrating foods



June 4, W 36.

F. W. Mg PHERRAN ET AL V EETHOD FOR DEHYDRATING FOODS Filed June 9, 1945 (dec ea sed) PHEFRRAN N m m R OE TH NP E v AA, M C 0 n 0 Hiiillllll WI MW ATTORNEYS I Y Patented June 4, 1946 UNITED smrs PATENT osmos- Friedericke W. Maclherran, Milwaukee, Wis., and

Charles C. MacPherran, deceased, late Milwaukee, Wis., by Nancy Ann Van Ells, administratrix, Milwaukee, Wis., assignors t NancyAnn Van Ells, Milwaukee, Wis.

Application June 9, 1945, Serial No. 598,486

" normal condition.

Incidental to the foregoing, a more specific I object of the invention resides in treating food products under conditions of relatively low temperature, and in the presence of products of combustion from charcoal, which serves as a color preservati n and effect... complete destruction of live organisms to prevent fermentation or mold. With the above and other objects in view, which will appear as the description proceeds, the invention resides in the novel method, construction, combination and arrangement of parts, sub stantially as hereinafter described, and more particularly defined by the appended claims, it being understood that suchchanges in the precise embodiment of the herein disclosedinvention may be made as come within the scope of the claims.

In the accompanying drawing is illustrated one complete example ofthe physical embodiment or" the present invention constructed according to the best mode so far devised for the practical application or the principles thereof.

In the drawing:

Figure l is a longitudinal sectional view of a forced draft dehydrator incorporating the principle oi the present invention; and

Figure 2 is an enlarged fragmentary section taken on the line 22 of Figure 1, illustrating a portion of one of the charcoal braziers.

While commercial dehydration of food is still in a state of development, some of the principles involved are well known, and accepted by authoritles and experts in the art. Therefore, it is considered unnecessary to enter'into a detail discussion-of the same, in view of which, the description of the present method and apparatus will he confined to only those conditions adeoted by the present invention.

Considering the method first, it is well recog= nized that in the practical dehydration of food, the material must be dried below the enzyme stage uniformly from center to surface. In utt lizing the term drying throughout the specification and claims, it is to he understood that lZ-Claims. (c1. 99-199) solution, which has been gradually brought to the same is employed in its restricted sense, designating desiccation or humidifying, and not mere drying of the materiaL'which results in mutilation or rupture of the cell walls, and consequently prevents restoration of the material to its normal state.

To accomplish the purpose of the invention, the material is first cleaned and prepared in the same manner that it would be prepared for ordinary cooking, after which it is severed into pieces. of uniform size and thickness, which insures uniform drying of the particles.

After preparing the material, the same is placed in a saline solution varying in strength to suit the requirements of the particular prodnot being treated, and it is important that the solution be brought to the same temperature as that of the material Inasmuch as it is desirable to retain the natural color of dehydrated products, in order that they may be subsequently restored to their normal appearance, it is proposed to add a small portion of sodium carbonate (NazCOs) to the saline solution.

The material may be left in the solution for a considerable period of time, approximately two or three hours without detrimental efiect, which results in adding moisture to the material to retard and prevent too rapid extraction of moisture from the material during initial subjection to the drying process. Also the added moisture prevents checking of the surface or superficial cells, and the formation of a glazed slnn dry surface to prevent the inner cells from liberating their moisture, leaving them subject to enzymio action. Throughout the entire initial treatment of the material, which is in a state'of nascence, outside influences should be guarded against, such as direct daylight, particularly sunlight.

After the material is removed fromthe saline the same temperature as the air to which the material is to be subjected, it is spread upon trays,

preferably made of wire mesh, and placed in the 1 depending upon the type of material being treat-- ed, and the initial temperature of the circulation of air should not exceed Fahrenheit. This creates a state of osmosis, which not onh' hastens 3 evaporation of the water, but allows its liberation with minimum effect upon the desirable ingredients'contained in the material.

During the initialaperiod of drying, as for example, the first hour, moisture is introduced into the circulated air, and thereafter, its humidity is gradually decreased to the desired degree, which usually requires approximately one hour and'a half.

One of the important features of the present method resides in subjecting the material durin treatment of the products of combustion from charcoal, which includes carbon dioxide (CO2), carbon monoxide (CO), and a small portion of sulphur dioxide (S02) which have no detrimental effects upon the flavor or texture of the material, but serve as insecticides and color preservatives.

The above process is continued until the material reaches a leathery state, in which moisture cannot be squeezed out of the end or freshly cut edges. When the material has reached the foregoing condition, the temperature of the circulated air is gradually increased, not to exceed 135 Fahrenheit at anytime, inasmuch as it has been found that high temperatures, or too long a period of subjection to heat, results in actual drying or cooking of the material, with'resultant rupture of the cell walls. I

When the treatment has been continued for a sufllcient period of time to bring the material to a brittle state in which it can be broken, it is removed from the dehydrator and placed in awell ventilated room at moderate temperature .and secured against the entrance of insects and the like. During the foregoing process, the water content of the material is sufficiently reduced to prevent fermentation or mold. However, sufllcient moisture is retained in the product to permit its restoration to normal condition by sub.- sequent addition of water.

The moisture content of the dried products may vary widely in different materials, some being able In the event that it is desired to reduce the mate- I rial to powdered form, the moisture left in the same is relatively lower than in whole pieces. Reducing material to powdered form is accomplished by passing the same through a grinder after it has reached a brittle state.

Finally the ground material is promptly packed in tight containers, due to the fact that in powdered form most material is hygroscopic, and. therefore, subject to cake if exposed to atmosphere.

Referring now to the drawing, the numeral l designates generall a forced draft dehydrator comprising an elongated casing 2, provided at its opposite ends with door or closure 3; The bottom of the casing 2, which constitutes a drying compartmentD, i provided at its opposite ends with doors or closure 3. The bottom of the casing 2, which constitutes a drying compartment D. is provided with longitudinal tracks 4, upon which trucks 5 equipp d with spaced rack 6 for the reception of trays, preferably formed of wire mesh and containing the material to be treated, are mounted. The trucks 5 are introduced into the cabinet at its forward end, which in the drawing is at the lefthand side of Figure 1, and during the dehydrating process the trucks are moved gradually toward the rear, or righthand 4 side of the casing and removed through the closure 3.

A horizontal longitudinal partition 1 terminating in an end wall 8 spaced from the forward end of the casing 2, forms an upper compartment 8 above the drying compartment D. Mounted in the compartment 9 is a motor driven impeller casing It! provided with an inlet ll communicating with the forward end of the drying compartment. The outlet end of the impeller casing communicates with an air passage or duct I2 through which air is circulated and introduced at the rear end of the drying compartment through which it is circulated in the direction indicated by arrows and returned to the impeller casing l0.

Positioned within the duct i2 is a pair of spaced conventional charcoal braziers l3, which may be charged through the sides of the casing 2, or in any other suitable manner. Consequently, air passing through the duct l2 will come in contact with the burning charcoal causing the same to be heated and mixed with the products of combustion with the charcoal for the purpose explained in connection with the method description.

In addition to the foregoing, the present method of heating the circulated air results in material operating economy, in that the heating medium is entirely contained within the casing 2 and the air is heated by direct contact with the fuel, rather than by radiation.

Inasmuch as it is desirable to recirculate only a predetermined amount of heated air, the duct i2 is provided with a partition I I, that carries a plurality of spaced nozzles [5, which forms an obstruction to the forced circulation from the impeller, and consequently, creates an increased pressure on the forward side of the partition,

which is employed to expel air through an opening it formed in the top of the duct 2 and controlled by a. slide plate II. The opening it provides communication between the duct and a discharge fiue l8.

To compensate for displacement of air discharged through the flue l8, an inlet flue i9 is positioned above the duct l2 and divided by a longitudinal partition 20 terminating in spaced relation to the rear wall of the casing 2, thus causing the incoming air to travel over an elongated circuitous path, after which it enters the duct l2 through an opening 2i formed in the top of the duct at the rear of the partition I, the openingll also being controlled by a slidabie plate l1.

Obviously, due to the action of the nozzles 15, which increases the velocity of air at that particular position in the duct, an injector action results, which serves to draw air from the duct which masses with the rear circulated air forced through the nozzles l5, thus permitting accurate control over both temperature and humidity of air circulated through the braziers and dehydrating compartment.

Obviously, humidity of the fresh air introduced into the dehydrator can be increased if desired by introducing moisture into the same in any conventional manner, and as a matterof fact, the present apparatus may be readily adapted to automatic control by means of a hygrometer to eliminate. the human factor.

From the foregoing explanation considered in connection with the accompanying drawing, it will be apparent that a simple method and apparatus have been devised for the most practical and inexpensive commercial dehydration of foods,

whereby their desired ingredients, normal texture and appearance are retainedto allow complete restoration.

What is claimed is: r

1. The method of dehydrating food consisting of cleaning and preparing the food as for cooking, then evering the same into particles of uniform size and thickness, next soaking the material in a solution of salt (NaCl) and sodium carbonate (NazCOa) of substantially the same temperature as the material, removing the material from said solution and subjecting the same to circulated heated air at relatively low temperature, containing products of combustion from a charcoal burner to impregnate the heated air with carbon dioxide, carbon monoxide and sulphur dioxide to preserve the color of the food product, gradually increasing the temperature of said air and reducing its humidity until sufficient moisture has been liberated from the material through the absorption f said air to reduce the material to a leathery state from which 6 no moisture can be squeezed, and then placing the material in a room of moderate temperature sealed against entrance of insects and until such time as the temperature of the material is reduced to atmospheric temperature. a

2. The method of dehydrating food consisting of cleaning and preparing the food as for cooking, then severing the same into particles of uniform size and thickness, next soaking the material in a solution of salt (NaCl) and sodium 

